/*
*  linux/kernel/mktime.c
*
*  (C) 1991  Linus Torvalds
*/

#include <time.h>

/*
* This isn't the library routine, it is only used in the kernel.
* as such, we don't care about years<1970 etc, but assume everything
* is ok. Similarly, TZ etc is happily ignored. We just do everything
* as easily as possible. Let's find something public for the library
* routines (although I think minix times is public).
*/
/*
* PS. I hate whoever though up the year 1970 - couldn't they have gotten
* a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
*/
#define MINUTE 60
#define HOUR (60*MINUTE)
#define DAY (24*HOUR)
#define YEAR (365*DAY)

/* interestingly, we assume leap-years */
static int month[12] = {
	0,
	DAY*(31),
	DAY*(31 + 29),
	DAY*(31 + 29 + 31),
	DAY*(31 + 29 + 31 + 30),
	DAY*(31 + 29 + 31 + 30 + 31),
	DAY*(31 + 29 + 31 + 30 + 31 + 30),
	DAY*(31 + 29 + 31 + 30 + 31 + 30 + 31),
	DAY*(31 + 29 + 31 + 30 + 31 + 30 + 31 + 31),
	DAY*(31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30),
	DAY*(31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31),
	DAY*(31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30)
};

long kernel_mktime(struct tm * tm)
{
	long res;
	int year;

	year = tm->tm_year - 70;
	/* magic offsets (y+1) needed to get leapyears right.*/
	res = YEAR*year + DAY*((year + 1) / 4);
	res += month[tm->tm_mon];
	/* and (y+2) here. If it wasn't a leap-year, we have to adjust */
	if (tm->tm_mon > 1 && ((year + 2) % 4))
		res -= DAY;
	res += DAY*(tm->tm_mday - 1);
	res += HOUR*tm->tm_hour;
	res += MINUTE*tm->tm_min;
	res += tm->tm_sec;
	return res;
}
